Preparation of insulin containing 2.75 to 8 percent zinc content



Aug. 27, 1963. H. M. CHRISTENSEN 3,102,077 I PREPARATION OF INSULIN CONTAINING 2.75 TO 87 ZINC CONTENT Filed Oct. 27, 1960 5 Sheets-Sheet 1 FIG I Henry Mar/nus Christensen INVENTOR JM, BY 1' W ATTORN EYS 20 Henry Mar/nus Christensen INVENTOR Jklmo ucr fut/H4 BY 1 PM Aug; 27, 1963 H.'M. CHRISTENSEN ,0

PREP AT QN OF INSULIN CONTAINING 2.75 TO 87 ZINC CONTENT Filed 001;. 27, 1960 5 Sheets-Sheet 2 FIG 2 0 M (I) O 2 I III 0.

(D Z I) O O 3 FIG 3 I! ll] (L V l l ATTORN EYS Aug. 27,1963 H. M. CHRISTENSEN 3,102,077

PREPARATION OF INSULIN CONTAINING 2.75 TO 8%ZINC CONTENT Filed Oct. 2'7, 1960 5 Sheets-Sheet 3 v FIG 4 77 O Zn 73 x I NI 0 Cd 72 9 v M g Q o I I I I l I I I I I l 7' O l 2 3 4 5 6 7 8 9 lo METAL ATOMS PER SANGER UNIT FIG '5 O 34 V v I Zn 33 x I NI O Cd 32 3 v I Mn 4 I l I l l l l I I l 0 3| 0 I 2 3 4 5 6 7 8 9 IO METAL ATOMS PER SANGER UNlT-- Henry Marinuschrisiansen INVENTOR ATTORN EYS Aug. 27, 1963 H. M. CHRISTENSEN PREPARATION OF INSULIN CONTAINING 2.75 TO 8% ZINC CONTENT Filed Oct. 27 1960 5 Sheets-Sheet 4 FIG 60 IIEO l I l 3 4 5 ZINC ATOMS PER SANGER UN|T FIG 6b o w w m m m o CELS IEMZUFZ ZOEUU EMI DMF EOMFZ 3 4 5 s ZINC ATOMS PER SANGER uN|T- Henry Mar/nus Chr/sfensen INVENTOR J hbulufi l W, BY ,L M

ATTORN EYS 7, 1963 H. M. CHRISTENSEN 3,102,077

PREPARATION OF INSULIN CONTAINING 2.75 T0 8% ZINC CONTENT 5 Shets-Sheet 5 Filed 001;. 27, 1950 l 2 ZINC ATOMS PER SANGER UNIT Au 6 l F l ZINC ATOMS PER SANGER UNlT-- Henry/Marinas Christensen INVENTOR W l BY p ATTORN EYS the insulin.

- August 2, 1954; 742,502 and 742,477 both filed on June 17, 1958 and 783,571 filed on December 29, 1958, all of which are now abandoned. i Y

It is the object of my invention to provide new zinccon-taining insulin compounds having a prolonged insulinetlect superior to that of the hitherto known zinc-containing insulin preparationsI It is a known art to produce insulin with increased zinc content in both crystalline and amorphous form by add- 1 ing insulin to aqueous media in which it is insoluble or only'slightly soluble and which contain a zinc salt and have a pH-value or 6-7, contingently with addition of up to 15% by volume of organic solvents, in order to dissolve the amorphous insulin and promote crystallization.

It is further known to prepare injectable suspensions or solutions of insulin. as well as insulin globin, insulin protamin', and insulin methylalburnin with different zinc contents and as well from insulin in amorphous as in crystalline form. The com-pounds can containup to a maximum of 2.2 to 2.3% zinc and corresponding amounts of some other. metals, such as .calcium, magnesium, manganese, iron, cobalt; nickel and cadmium bound to In the following there areespecially discussed new zinc insulin compounds, :as zinc is by far the most impor-tant, metal in combination with insulin. 1

Inthe hitherto known aqueous suspensions :of' 'such zinc insulins it has not been possible either by varying pH, adding a largesurplus of zinc, or by other meansto bring the chemicallybound zinc content of the zinc up over the stated maximum value.

Thejknown insulin is a preparation of the active antidiabetic principle of the internal secretion of the islands of Langerhans of the pancreas. It normally contains'0.4 to 0.9% of zinc, audit is possible to augment this zinc content up to 2.3% by treating the normal insulin with zinc salts in the above said aqueous media.

In the animal body, thehighest concentration of zinc is found in the pancreas. Moreover, zinc is invariably present in all samples of crystalline insulin. In fact, it has been reported that it is impossible tocrystallize insulin in the absence of zinc, nickel and cadmium, which normally are found in pancreas, and some other metals such as calcium, magnesiurmmanganese, iron and copper.

Such zinc-containing insulin and methods for its production have been described, for instance, in the patents to Petersen et al. Nos. 2,882,202 and 2,882,203 issued both on April 14, 1959. Zinc-insulin compounds having,

varying zinc contents in the order of 2% by weight and maximally 2.7% are'described in these patents. However, the zinc content in these products exceeding 2.2 to 2.3% is not chemically bound, but only adsorbed or occluded, Le. not built in a regular pattern in the lattice of the zinc insulin elementary cell, as is demonstrated by the following facts. I

When. theknown crystalline or amorphous zinc insulins after being isolated are suspended in water or known buffer solutions for injection, they will all give oii zinc United States PatentjO v technique of zinc-insulin preparation can beconsiden to the water in a quantity bound 'to the insulin. However, it has never been 'possible in any hitherto known aqueous suspension of zincinsulinamorphous or crystalline-to maintain "InQ Te than 2.2 to 2.3%' zinc chemically'bound to theinsulin; Thus insulin With a chemically bound content of 7% zinc will when suspendedfin zinc free Water to a concentration of e.g. 40 international units per ml. dissociate almost 1 water to the said concentration it will dissociate. 0.8 to

0.9% zinc.

The importance of the zinc content in insulin has long been known, and in practice use'has been made of suspensions in Water of zine-insulin with about 2% 'zinc chemically bound to crystals and tdam-orphous' insulin.

Both forms are insoluble and retain up to about 2.2%

zinc content in water with pH 7 in the presence of a surplus of zinc ions.

' The insulin preparations herementioned have, *when injected into diabetic patients, had aretarded eifec't ofup to 36 hours in some cases; But in practice one is,"on

practical grounds, satisfied with an eiiectof 24 hours. I have now discovered thatthis present stage of the ably improved by producing, for example zinc-insulin in amorphous or crystalline form with a chemically bound zinc content of as high up as 6% and even up to about In the known processes, insulin and a water-soluble Zinc salt such as zinc chloride are reacted inwater as the reaction medium. For promoting the crystallization,

. only mixtures of water have beenused, such mixtures being maximally about 15% by volume of organic 'sol vents, at a pH of about 4 to 8 preferably between 5.0 and 7.0. These processes lead to the formation of' Zinc insulins in which maximally two zinea'toms-are chemically bonded to the acid groups of the insulin linolecule, by replacing hydrogen-atoms of the carboxylici groupsorj to the imidazole rings of the aforesaid hi-stidyl residues.

(Waitzel, Angewandte Chemi '68, 569 (1956) citing K. Hallas-Miiller et al. Ugeskrift f. Laeger SZ, 1761 (1951).)

Under the above-mentioned conditions of the known processes, the aflinity of the zinc to the insulinis greater than the afiinity of the zinc for the acid or hydroxyl groups from the aqueous reaction medium, until about 2.3% by weight of zinc has been bound in the abovedescribed manner by insulin corresponding to about 2.2 gram atoms of zinc per mole of .zinc insulin. By the known methods it was thus possible to prepare zinc insulin with a content of, in practice, about 2.6% of zinc vention makes it possible'to prepare new zinc-insulin compounds which contain from about 2.3 up to 8% of zinc chemically bound in a different manner to the insulin.

These unexpectedly high zinc contents in zincinsulin,

i and a highly superior pro-longed effect of" the "new Zinc.-

insulin compounds, are obtained'surpris'ingly'by the proc} ess accordingto my present invention which comprisesre acting insulin with soluble zinc salt. such'as, preferably, zinc chloride, or zinc bromide or zinc ace'tatd ina 'solution in a solvent which is chemically inert to insulin and p to the new zinc-insulin compound being formed, and which solvent is selected from the group consisting o-fz Anhydrous lower alkyl alcohols such asmethyl alcohol, ethyl alcohol, propyl alcohol; aqueous ,mixtures of the same alcohols having an alcohol content of above Parmesa 27,: was

related to the Zinc originally V tinder sterile-conditions.

tals of.

Anhydrous lower aralyl alcohols such as benzyl alcohol;

it Arrhydrouslowermononucleararyl compounds having direetly substituted hydroxy groups alone or together with.

lower alkylsubstituents at the benzene ring, such as phenol, cresols and the like;- 4 I Weake organic nitrogen-containing bases such pripending on the. composition of the zinc salt used, which mary loweralkyl amines and pyridines; Ithese last-mentioned basesmay also be used in mixture with water, and

ammonianmmonium chloride complex compound,

' NH .NH Cl I which is added in order to avoid the formation andprecipitati on of zinc hydroxide;

Finally, there can'be used asso'lvents lower carboxylic acids such as glacialacetic acid, propionic acid, 'glycolic acid andlactic acid, again, when used in' mixture with water, preferably, in the. presence of the aforesaid amnwnia ammonium chloride compound. :Whenever the abovedescribed solvent contains water, thefamount of .the latter in the solventmixture must al 'vvay's beless than 85% and in tmost cases less than 50%.

] To; summarizeanyyorganic solvent is suitable for the process'pf my'invention, if it does not react .withinsulin randthe' zinc insulins being formed, and if it is a solvent for the zinc salt used in the reaction with insulin. According to another feature of the invention, the sol- 'vent used is one in which the insulin is soluble; the insul'iri caii also b'e used in solution in a, mixture of several ot the said solvents;

1 According to an tion, insulin is broug'hbin solid form into reaction with one of the, described zinc salt solutions by. suspending it therein. The crystallineor amorphous insulin particles V will easily combine withthe dissolved zin'c compounds.

tation or zinc hydroxide;

f, entire process may, of course, be carried out Thejresul't of .the present method is that, injcontradis- JtLIICfiO HLtO previously known methods, it is possible in a reliable and simple mannerto control the quantityof :zincadsorbed in the insulin and, more particul'arly ,,to

prepare"e.g. crystalline zinc chlorine insulins with increased content of zinc suspended eg in g'lyceridcs'of the tatty' acids and vastly prolonged antidiabetic efiect.

whentc'rystallinezinc chlorine insulins containing 2.3

to"about8% of zinc are. suspended in zincfree water to at-concentration of 40 i.'u. per ml. they separaterinc "chloride. 'IfJthe'ZincchIorine insulin contains 2.3% to about 5. or 6% zincthe remaining precipitate of zinc insulin will containflA to 2.3% zinc. .[I f zinc chlorine insnlin containing higher "zinc contents than the said 5 to 6%) o'r' zinc, the precipitate of zinc insulin will retain f n 2.3% ofizincf' Ilnlthe process according to my inventionthe reaction mixture. containing the two main reactants, i.e. insulin andthein'e'tal salt, as well 'asthe solvent is stirred for some time, usually 'forsome hours, the precipitated crysa new zincjinsulin or corresponding other metal insulin esepar'ated; for'instance by filtration, washed with: the solvent or, 1 preferably, with absolute ethyl alcanal, and finally d ied. v e a new zinc compounds prepared according to the; :a'bo edescribed process of my invention differ from the zinc insulins in a number 'of features: In the insulinnioleculethere are fbondedzino atoms inamount ranging fIOm BJbOVB 2.3 to about 8% by weight pre'ferably, in the latter case, in the-presence of an:

both the new land the known zinc insulins with increasing other mode of the process of the totem per mole of zinc-insulin.

P un ranges from about 3 or less t9 12 gram atoms of halogen This halogen content corresponds stoichiometrically to the content of zinc or other metal gram atoms exceeding 2 inthe new zinc insulins.

V The new zinc-insulins differ significantly from the known ones, in. their crystallographic characteristics, in

that the lattice constants determined by X ray diffraction vary differently from, those, of the known zinc insulins with changes of the zinc content. For instance, ,whi-le'tihe a-axis of the" elementary crystal cell increases slowly in per zinc insulin moleculeJand then remains substantially constant at 33.3 to 33.5 angstroms up to the maximum content of about 8 gramatoms of zinc in the new com- The new compounds with the highest zinc content have been found to correspond to the stoichiometrical composition InsulinZn C-l Other compositions deter mined thus far are Insulin.Zn Cl and Insulin.Zn Cl The general formula torthese compounds is therefore InsulinZn J X- wherein X is a monowalent anion, preferable chlorine, and m is a positive number up to and including 6. A zinc insulin bromide and a zinc insulin acetate have also been produced by using as starting material zinc bromide and insulin or zinc acetate and .insulimrespectivdy. The mionovalentanion X in the tformula given above need therefore not be a (halogen, but can also be acetate.

All percentages given in this application are by weight calcuated on the basis of the total weight of the respective new zinc insulin compound produced, e n p p The fiormul as of the new compounds were calculated as follows: n p n M The molecular weight of the insulin portion of the new compounds was. set at about 6000 which is the Sanger unit of 5778 plus 6% added to take into account the, water content of dry insulin. This water is not water of crystallization since it does noteifect the lattice constants discussed hereinbefore, i.e. it is not settled periodically in the lattice.

The total molecular weight P of the new zinc insulins having the general formula Insulin.Zn X is therefore," in rounded figures (atomic weight of zinc=65) V I (I) P=6000+ (rm+2).65+2m.X"

X being the atomic or molecular weight of therespectivc anion. The number of atoms of zinc in the new zinc insulin molecule can be calculated from the determined percentage by .weight y of zinc in the new compound as follows. The zinc content corresponds to the formula:

- Resolving this equation for P and setting the left side of this equation equal to the right side of Formula I for P above yields the following equation ifor m:

the value of m in Formula III is zero. This corresponds perfectly to the saturation value of 2.2 for zinc incorporated in insulin which has been mentioned frequently in the recent literature (see Weitzel, supra.)

The above-mentioned crystallographic data as well as other properties of the new compounds are illustrated by the graphs shown in the accompanying drawings of which FIG. 1 is an X-ray powder diagram of air-dried zincinsulin crystals. containing 6.8 atoms of zinc per mole (Sanger unit) of insulin. Using automatic recordings, the innermost part of a powder diagram taken with Geiger- Mueller difiractometer was traced from 29=2 to 2G=6. CuIQa radiation was applied, with automatic recording.

FIG. 2 is an X-ray powder diagram of the same material as used in FIG. 1 and under the same conditions, but with a stationary 120-second counting at intervals of 0.5 to 010 in 26.

FIG. 3 is a powder diagram of air dried zinc-insulin crystals of a zinc content as used in FIGS. 1 and 2, and taken under the conditions of FIG. 2, but with 29 rangingfrorn 6 to 11.

FIG. 4 is a graph illustrating the above-discussed variation of the a-axis of the elementary cell'of zinc-insulin crystals with varying zinc content.

FIG. 5 is a graph illustrating the above-discussed variation of the c-axis of the same elementary cell with varying zinc-content, and

FIGS. 6a to 6d are graphs showing the integrated reflection intensities with increasing zinc content for the innermost lines in the powder diagram shown in FIG. 3 above.

These last-mentioned figures show integrated intensities measured as peak area over a smoothed background. Curves 6a, 6b, 6c and 6d indicate a break at about 2 zinc atoms per insulin molecule and curves 6b, 6c or 6d another break at about 4 atoms of zinc per zinc-insulin molecule, which confirms the above-described changes in the, length of the c-axis of the zinc-insulin elementary cell with increasing zinc content. No significant variation occurs at higher values. p I

The break at 2 atoms of zinc has been explained above as being due to the fact, confirmed by chemical analysis,

that at this point the reaction between insulin crystals and for instance, the organic zinc chloride solution according to the process of my invention sets in, as a simultaneous incorporation of zinc and chloride ions in the insulin molecule, while below the limit of about 2 atoms of zinc per molecule, exclusively zinc is incorpated by ion exchange for hydrogen from the insulin carboxylic acid groups.

The first two zinc atoms taken up together with stoichiometrically corresponding amounts of chlorine in the range above the minimum of 2 and up to the second break corresponding to a total content of 4 zinc atoms in the new zinc-insulin molecule are also placed in fixed positions in the elementary cell. Otherwise, the drastic changes inreflexion intensity shown by graphs 6!), 6c and 6d would not occur. These novel products having a zinc content above 2 atoms per molecule and a chlorine content of 2n atoms for every n zinc atom in excess of 2 are therefore chemical compounds.

The reaction between insulin crystals and soluble zinc salts in preponderantly organic, inert solvents, according Insulin.Zn zm in which, for this second stage, In is a positive number Insulin.Zn Cl "in the third stage, further zinc and anions are incorporated in the zinc insulin, however, in a different manner which is characterized by the fact that the caxis of the elementary cell remains constant at about 33.3 angstroms, while the a-axis continues to increase, and that the reflexion intensities in this range remain also constant (FIGS. 6b, 6c and 6d).

On the other hand, the single break in the curve of FIG. 6a shows that the novel compounds with above 2 up to about 8 Zinc atoms and with anions, according to the invention, have common properties which differentiate them from the known compounds having up to about 2 atoms of Zinc per zinc-insulin molecule, but no anions incorporated therein. The new zinc compounds may also be formulated as InsulinZn (ZH Z) q wherein q is a positive number up to 6.

While the first above-described stage must be considered an ion-exchange process, the second stage can be explained as yielding compounds of interstitial or superphase structures, and the third stage as an absorption stage leading to the formation of double salts or additive compounds. The formation of these different groups of compounds was not to be expected, since the entire reaction seems to follow an adsorption isotherm as described by K. Marcker in Acta'Chemica Scandinavica 13 (1959), particularly FIG. 1 on 2037. The process of my invention is also applicable to the formation of novel metal-insulin compounds containing anions in which a large portion of the zinc, or substantially all, has been replaced by other metals, namely calcium, magnesium, cadmium, manganese, iron, nickel or cobalt. Some of [the compounds prepared in this man ner are defined by the following formulas:

(Insulin) Zn.Mn (MnCl 7 MnCl zinc-dodecamanga- The starting material for the formation of these new metal insulin compounds containing metals other than zinc is preferably a zinc-insulin having at least the well known minimum zinc content required for crystallizing insulin. The starting zinc-insulin is'suspended in an organic solution of the other metal compound, for instance, nickel chloride, manganese-(II)-chloride, cadmium chloride, cobaltous chloride, or ferrous chloride, or the respective soluble salts of other monovalent ions such as bromide or iodide.

Table 3 below gives the chemical composition and X-ray characterization of compounds formed when crystalline zinc-insulin is suspended in an cthanolic solution zinc-decacadmium-decachloof another heavy metal chloride.

Metal chloride Me atoms/ Zn atoms/ a (A.) c (A.)

unit unit 2. 8 0. 5 76. 5 33. 6 8.8 0.4 77.3 34.1 5. 4 0.3 71 34 7. 8 0. 1 Untreated 0 0. 7 74. 1 32. 4

I The practical importance of the invention is, that when in the treatment of diabetic patients one uses the produced aqueous metalinsulin suspensions-either of crystalline or amorphous insulin as well as mixtures of these insulin formswith a metal content that one practically oneself can choose, and which e.g. in the case of zinc lies above the hitherto known maximum and used content of 22-23%, by varying the bound quantity of metal, one canobtain an undreamt of, durable controllable retarded efiect of insulin preparations, for instance of 72 hours and longer. 1

One has thus found a quite considerable retarded efiect, already with preparations with above 2.5 to about 4.5% (calculated on the weight of insulin) chemically bound zinc in the new zinc insulin crystals or in corresponding amorphous zinc insulin in suspension.

"Without being bound to the exact atomic arrangement of the elementary cells of the new zinc-insulin compounds, all presently available data point to the following structural arrangement of the metal atoms relative to the characteristic histidyl groups in the new zinc insulins ofabove 2 to 8 zinc atoms according to Formula 1 as compared with the known zinc msulins which may comprise an arrangement according to Formula 2:

(IHSllHILZmCh) NH: N112 orzmooo-on-on ;on bn-ooo.zu.01

011: remaining C=CH OI.Zn.N I rh ril c i r le I N.Zn.Ql

CH=N =0 7 (InsulinZnr) (2) NHi NH:

ooo-a'zn-on on-r sn ooo on=o remaining 0:011 Y insulin Zn-N l molecule I NZn oH=o N=o My invention is further illustrated but not limited by a number of examples given hereinafter. All percentages are by weight and based on the total weights of the resulting new zinc insulins. i

Example 1 1 g. of crystalline insulin is suspended in 100- ml. of "absolute ethyl alcohol containing mg. zinc per ml. in the form of zinc chloride. After stirring for two hours, the resulting crystals-are isolated by filtration, washed with ethyl alcohol and dried. They contain about 5% of zinc and about 3.3% of chlorine based on the total weight of the resulting zinc insulin. As an alternative the crystals may be isolated by centrifugal separation. The above zinc content corresponds to about 5 atoms of zinc per insulin weight. The formula IllSlllllLZl1 Cl Dl' written in a difierent manner, Insulin.Zn- (Zn Cl can thus be attributed to the above obtained new compound. The molecular weight based on a weight of the insulin portion of 6000* is about 6540 for the unassociated molecule.

Example 2 Example 3 *1 g. of crystalline insulin as used in Example 1, is

"suspended in 100 ml. absolute ethyl alcohol containing "5 mg. zinc per ml. in theform of zinc chloride. After stirring for two hours the resulting crystals are isolated I as above, washed with ethyl alcohol and dried. They contain about 3.5% of zinc and about 1.6% of chlorine.

associated molecule is about 6250. If only 1 mg. zinc per ml. is used the resulting crystals contain only about 1.5 percent of zinc and no chlorine at all. 1

Example 5 ,1 g. crystalline insulin is suspended in g. molten, anhydrous phenol containing 1 percent zinc in the form or ZnCI After stirring for two hours, an equal volume of ethyl alcohol is added, the crystals are isolated as above, washed with ethyl alcohol and dried. The crystals contain about 5 percent zinc and about 3.3% of chlorine.

Example 6 1 g. crystalline insulin is suspended in 100ml. benzyl alcohol containing 20 mg. zinc in the form of ZnCI After stirring for two hours the crystals are isolated as above, washed with ethyl alcohol and dried. The resulting crystals contain only about 2 percent zinc and no chlorine. The example is repeated augmenting the zinc content in the solution to 40 mg. Crystals are obtained which contain about 4 percent of zinc and about 2.1% of chlorine.

Example 7 1 g. crystalline insulin is suspended in 100 ml. acetone containing 5 mg. zinc per ml. in the form of zinc chloride. After stirring for two hours the crystals are isolated as above, washed with acetone and dried. The crystals contain about 5% of zinc and about 3.25% of chlorine.

Example 8 1 g. crystalline insulin is suspended in 100 ml. of a mixture of alcohol and water containing 35 percent by volume of ethyl alcohol. The mixture contains 10 mg. zinc per ml. in the form of zinc chloride. The solution has a pH-val-ue of 4.5. After stirring for two hoursthe crystals are isolated as above, washed with ethyl alcohol and dried. The crystals have a zinc contentof about 3.5 percent and about 1.6% oii chlorine.

If the alcohol-water mix-ture contains 20 percent by volume of ethyl alcohol and 1 mg. zinc per ml., and the process is performed at a pH-value of 4.7 the resulting zinc-insulin crystals show only :a zinc content of about 1.7 percent, but no chlorine content.

Example 9 1 g. crystalline insulin is suspended in 100 ml. of a mixture of alcohol and water containing 15 percent by volume of ethyl alcohol. The mixture contains 10 mg. zinc per ml. in the form of zinc chloride. After stirring for two hours the crystals are isolated as above, washed with ethyl alcohol and dried. The resulting crystals show a zinc content of only about 2 percent, but no chlorine, due to the high water content of the solvent.

Example 10 1 g. crystalline insulin is suspended in 100 'ml. of a mixture of alcohol and water containing 50 percent by volume of ethyl alcohol. The mixture contains 10 mg. per ml. of zinc in the form of zinc chloride. To the mixture is added asolution of NH NH Cl in order to obtain a pH-value of 7. After two hours stirring the crystals are isolated as above, washed with ethyl alcohol and dried. The crystals contain about 7 percent zinc and about 5.3% of chlorine. new zinc insulin is about 6860 for the unassociated mole- The molecular weight of the.

cule which corresponds approximately .to the formula insulinZn 4.

Example 11 'l g. crystalline insulin is suspended in 100 ml. of a mixture of water and alcohol containing 35 percent by volume of ethyl alcohol. The mixture contains mg. Zinc per ml. in the form of zinc chloride. To the mixture is added a solution of NH NH Cl in order to obtain a pI-I-value of 7. After stirring for two hours the crystals are isolated as above, washed with ethyl alcohol and dried. -The crystals contain about 5.5 percent zinc and about 3.5% of chlorine.

Example 12 Example 13 ,1 g. crystalline insulin is suspended in 100 ml. 30 weight percent aqueousethyl alcohol, containing 2.3 mg. zinc per ml. in the form of zinc chloride and having a pH- value of 4.4. The insulin is partly dissolved. The undis solved portion of the crystals are separated by filtration, washed with ethyl alcohol and dried. They contain 2.2 percent zinc. The pH-value of the filtrate is brought to 6.3. Amorphous insulin is precipitated and washed with ethyl alcohol and dried. The amorphous in sulin has a zinc content of about 4.5 percent and about 2.75% of chlorine.

Example 14 l g. of crystalline insulin is suspended in 100 ml. of absolute ethyl alcohol containing 5 mg. zinc per mil. in the form of Zinc bromide. After stirring for three hours at room temperature (25 C.), the resulting crystals are insolated by filtration, washed with ethyl alcohol and dried. They contain about 5% of zinc and about 7.5% of bromine. The molecular weight of the new Zinc insulin is about 6855 for the unassociated molecule. Its composition approximates the formula Insulin.Zn Br Example 15 Example 14 was repeated, but using zinc acetate instead of Zinc bromide. The resulting crystals contained 5% zinc and about 2 of acetate ion.

In all the above examples amorphous insulin may be used instead of crystalline insulin.

Instead of zinc as used in the above examples calcium, magnesium, nickel, manganese, cadmium and cobalt may be used. The amounts of these metals thereby bound to the insulin correspond to the figures given in the above examples for zinc and also for instance to the figures appearing in Table 3.

What is claimed is:

1. A process for the production of crystalline zincinsulin compounds having a content of monovalent anion selected from the group consisting of chloride, bromide and acetate corresponding stoichiometrically to two gram atoms of heavy metal less than the total amount of gram atoms of said, heavy metal present in said metal-insulin compound per mole thereof, which process comprises reacting insulin with the salt of said monovalent anion and a heavy metal selected from the group consisting of Zinc, calcium, manganese, cobalt, magnesium, iron, nickel and cadmium in a solvent for said salt, said solvent being chemically inert to insulin and to the for-med metaleinsulin compound and being selected from the group consisting of anhydrous lower alkyl alcohols, aqueous mixtures of lower alkyl alcohols, anhydrous lower aralkyl alcohols, unsubstituted and lower alkyl-substituted phenols, anhydrous pyridines, aqueous pyridine mixtures alone and in mixture with ammonia-ammonium chloride, lower monoand di-basic fatty acids and mixtures of said fatty acids with water alone and together with an admixture of ammonia-ammonium chloride, the content of water in said mixtures with lower alkyl alcohols, with pyridines and with said fatty acids, respectively, being less than 85% by volume.

2. A process as described in claim 1 wherein the start ing insulin is crystalline insulin.

3. A process a described in claim 1 wherein the starting insulin is amorphous insulin.

4. A process for the production of zinc-insulin containing from about 2.75 to about 8% by weight of chemically bound zinc and chlorine in stoichiometrically proportion to two gram atoms of zinc less than the total number of gram atoms of zinc present in said zinc-insulin per mole thereof, which process comprises reacting insulin with Zinc chloride in solution in a solvent for the latter, said solvent being chemically inert to insulin and to the formed zinc-insulin and being selected from the group consisting of anhydrous lower alkyl alcohols, aqueous mixtures of lower alkyl alcohols, anhydrous lower aralkyl alcohol, unsubstituted and lower alkylsubstituted phenols, anhydrous primary lower alkyl amines, anhydrous pyridines, aqueous pyridine mixtures alone and in mixture with ammonia-ammonium chloride,

lower monoand di-basic fatty acids and mixtures of said fatty acids with water alone and together with an admixture of ammonia-ammonium chloride, the content of water in said mixtures with lower alkyl alcohols, with pyridines and with said fatty acids, respectively, being less than by volume.

5. A process for the production of zinc-insulin containing from above 2.75 to about 8% by weight of chemically bound zinc and chlorine [in stoichiometrical proportion to two gram atoms of zinc less than the total number of grant atoms of zinc present in said Zinc-insulin per mole thereof, which process comprises reacting insulin With zinc chloride in absolute :ethyl alcohol.

6. A process for the production of zincdnsulin containing from above 2.75 to about 8% by weight of chemically bound zinc and chlorine in stoidhiometrical proportion to two gnainr atoms of zinc less than the total number of gram atoms of zinc present in said zinc-insulin per mole thereof, which process comptises'reacting insulin with zinc chloride in solutionin an aqueous ethyl alcohol solution containing about 15 to 50% by fonrnula of ethyl alcohol.

7. A process for the production of zinc-insulin containing from above 2.75 to about 8% by weight of chemically bound zinc and chlorine in stoichiometrical proportion to two gram atoms of zinc less than the total number of gram atoms of zinc present said Zinc-insulin per mole thereof, which process comprises reacting insulin with Zinc chloride in solution in an aqueous ethyl alcohol solution containing about 15 to 50% by volume of ethyl alcohol and ammonia-ammonium chloride.

8. A process for the production of zinc insulin containing 2.75 to 8% of chemically bound zinc, which comprises reacting insulin with zinc chloride in solution in 'a solvent for the latter, said solvent being chemically inert mining-from 2175 to 8% of chemically bound zinc, which I comprises intimately admixing insulin with corresponding amounts of a soluble zinc salt and with NH -NI-I O1 in solution in a solvent selected from the group consisting of glacial acetic acid, lactic acid, glycolic acid and pmopionic acid, said solvent being inert to the insulin and to the resultant zinc insulin, and said solution containing less than 85% of water, whereby reaction takes place and the desired zinc insulin with 2.75 to 8% of chemically hound zinc separates out.

v11. A puocess fior the production of zinc insulin containing from 2.75 to 8% of chemically bound zinc, which comprises intimately admixing insulin with a corresponding amount of a soluble zinc salt in solution in pyridine, said solution containing less than 85% of water, whereby reaction takes place "and the desired zinc insulin with 2.75 to 8% of chemically hound zinc separates out.

References Cited in the file of this patent UNITED STATES PATENTS 2,882,202 Peterson et al. Apr. 14, 1959 FOREIGN PATENTS 786,635 Great Britain Nov. 20, 1957 OTHER REFERENCES Hallas-M olier et iaiL, Science 116 (3015), pp. 394496, Oct. 10, 1952. 

1. A PROCESS FOR THE PRODUCTION OF CRYSTALLINE ZINCINSULIN COMPOUNDS HAVING A CONENT OF MONOVALENT ANION SELECTED FROM THE GROUP CONSISTING OF CHLORIDE, BROMIDE AND ACETATE CORRESPONDING STOICHIOMETRICALLY TO TWO GRAM ATOMS OF HEAVY METAL LESS THAN THE TOTAL AMOUNT OF GRAM ATOMS OF SAID HEAVY METAL PRESENT IN SAID METAL-INSULIN COMPOUND PER MOLE THEREOF, WHICH PROCESS COMPRISES REACTING INSULIN WITH THE SALT OF SAID MONOVALENT ANION AND A HEAVY METAL SELECTED FROM THE GROUP CONSISTING OF ZINC, CALCIUM, MANGANESE, COBALT, MAGNESIUM, IRON, NICKEL AND CADMIUM IN A SOLVENT FO SAID SALT, SID SOLVENT BEING CHEMICALLY INERT TO INSULIN AND TO THE FORMED METAL-INSULIN COMPOUND AND BEING SELECTED FROM THE GROUP CONSISTING OF ANHYDROUS LOWER ALKYL ALCOHOLS, AQUEOUS MIXTURES OF LOWER ALKYL ALCOHOLS, ANHYDROUS LOWER ARALKYL ALCOHOLS, UNSUBSTITUTED AND LOWER ALKYL-SUBSTITUTED PHENOLS, ANHYDROUS PYRIDINES, AQUEOUS PYRIDINE MIXTURES ALONE AND IN MIXTURE WITH AMMONIA-AMMONIUM CHLORIDE, LOWER MONO- AND DI-BASIC FATTY ACIDS AND MIXTURES OF SAID FATTY ACIDS WITH WATER ALONE AND TOGETHER WITH AN ADMIXTURE OF AMMONIA-AMMONIUM CHLORIDE, THE CONTENT OF WATER IN SAID MIXTURES WITH LOWER ALKYL ALCOHOLS, WITH PYRIDINES AND WITH SAID FATTY ACIDS, RESPECTIVELY, BEING LESS THAN 85% BY VOLUME. 